Roof direction in skillion roofs

Is there a tool to accurately determine roof directions while editing? My approximations dont look good while rendering. An example is (britam tower in nairobi)

I always use JOSM to determine the correct roof direction. I draw a 90° angled line in the direction of the rain, and the number my arrow points to is the roof:direction of the skillion.

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Wow!
Thanks for that. Which josm tool do you use for that?

Most times, the direction is calculated by the longest side automaticly. A „roof:orientation=across“ may be needed.
Your example looks complex and a degeree would be the saver tagging.

This is standard line drawing (press a, click on the line you want to draw a 90° angle from, press a again. You’ll notice that the angle symbol becomes green when you press a that second time, and the text “Angle snapping active” is added:

image

Now hold ctrl and hover over that line until it’s marked yellow:

Now moving your mouse around will snap at certain angles, as you can see on my very first screenshot with the dotted yellow line.

That doesn’t work for roof:shape=skillion, only for symmetrical roofs.

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What renderer do you use? Example way id?

I’m not using a specific renderer, but I’m testing most of my changes in OSM2World. Just quoting the wiki regarding roof:orientation if you don’t believe me:

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Well of course for squares don‘t have a defined „longest“. But your example abowe isn‘t one.

Thanks alot for the help! :beers:

It’s not square, it’s about the roof’s shape, which is a skillion:

You quoted the OSM wiki: orientation and skillions don’t work “for squares”. Normally it works.
If you get me the OSM id I would do some checks.

It says

In the case of pent roofs (skillion ) […], capturing with roof:orientation is not suitable; roof:direction must be used here.

It cannot work, because the roof:orientation describes the orientation of the roof ridge. Since skillions are pretty much “one side of a hipped roof”, you still need to say which side :slight_smile:

Well, you dropped “and square buildings”. Only square buildings don’t work.
Sure, a skillion does not have a ridge, but a high corner, which is the same in this case.
And if a gabled building is an exact square, the orientation will have the same trouble
because the result is mathematical near undefined and may depend of the system, interpreting the Way.

I do write 3D rendering myself. Please give me an example ID to check it.

Oh, I just had a 2nd look at the wiki:
https://wiki.openstreetmap.org/wiki/Key:roof:orientation
“pent roofs (skillion ) and square buildings”
The “and” in this case may not be meant boolean, but a human OR.
Anyway, I don’t see why it should be a problem. Please show me examples.

No, neither square roofs nor skillion roofs work. I dropped the square, because you were misquoting me.

Exactly. But you still don’t know which side that goes down that ridge you want to render: left or right. It only works for roofs which are symmetrical left and right the ridge, because then you can render both.

For for peace of mind, here’s the ID of a building:part with a skillion: 1091004491. Of course you have a 50% chance to render the correct half of the roof…

O, I see: If it is an exact rectangle, the “longest side” is still near undefined. And for me, the longest side is the one, a skillion goes down from. Your example is quite clear about the longest side. So a renderer, following “My Rules” :wink: will solve it.

In Passau are many skillions without directions. What do all renderer / OSM2World do? Follow “My Rule”? :wink: But that’s just a “backup”, the Wiki is a good advice anyway.

Hello,
Can anyone assist me in modelling of britam tower in nairobi. Ive tried this method but still does not look good. Just search britam tower in nairobi upper hill. Same with (rahimtulla tower)

The construction with building:part scillion is quite unusual, but looks almost correct.
I think the square symmetry of the parts is not exact, so the upper “ceiling” of them is not exact at the inner square. We need to have an WYSIWYG editor.

https://www.osmgo.org/v03.html?km=1&lat=-1.29984721&lon=36.81380474&ele=158.69&dir=95&view=-54

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The effect of forgetting that the ‘terraced’ houses opposed to the terrace outline have an across gabled roof instead of along, for the terrace as a whole. Combined with the underground parking underneath, entrance for the whole at the far west, thus building:levels:underground=1, it became a really low lying set of 15 abodes, townhouses whatever the local lingo calls these.

Don’t do much in building splitting just because the architect slaps an assortment of roof designs together.

Windmill skillion is interesting, 1 house 4 roof directions. The OSM roof wiki says the 3D modelling will be ready soon for this and the double_gabled (since a few years)

For double_gabled I’ll tag roof:orientation=along and in the example roof:direction=SW (I mostly use general compass, the renderers can figure out on a square box in any particular orientation that SW tells where the low side is. But, there’s a roof here where the gable is diagonal on a church… could not get it to render correct even when splitting the roof in 2, so it became bloodied white towel in the ring. Guess the 3D render modellers, more likely my skills are, not ready for these.

Note that the upper square is rotated 90 degrees from the lower one… maybe i should use exact squares, shrink one then rotate. Seems more like technical drawing

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